Wireless Power Line Sensor

ABSTRACT

A wireless sensor apparatus for determining and reporting the status of an electrical wire, said sensor apparatus comprising: an electrically insulated housing; a non-contact electrical energy harvesting device, said energy harvest device disposed within said housing, said energy harvesting device comprising an electric current detector and voltage detector; an electric power source, said power source operatively connected to said energy harvesting device; a microcontroller, said microcontroller operably connected to said power source; a mechanically rigid base, said base operably connected to said housing and to said at least one strain gauge, said at least one strain gauge operably connected to said power source and to said microcontroller; a wireless data transmission antenna, said wireless data transmission antenna operably connected to said power source and to said microprocessor; a visual indicator, said visual indicator operably connected to said power source and to said microcontroller.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional of U.S. patent application Ser. No. 14/599,749,entitled “Wireless Power Line Sensor”, filed Jan. 19, 2015, which isincorporated herein by reference.

BACKGROUND

1. Field of the Invention

The present invention relates generally to systems, methods, andapparatuses for determining the mechanical load and electrical energystatus of a wire. More specifically, the present invention relates tothe use of a non-contact sensor within an insulator to determine theelectrical and mechanical “status” of a utility power distribution line.

2. Description of the Prior Art

The impact of severe weather events on critical infrastructure can havedevastating impacts. With regard to the electricity subsector, 90% ofall power outages occur on the distribution system. Severe storms andnatural disasters can cause a variety of safety hazards including downedpower lines which create a dangerous environment for those working torecover from the damages of a weather event. Downed power lines maystill carry live, high voltage electricity. Contact with a downed,energized power line can cause severe injury or even lead to fatality.Safety is of utmost concern to the electric utilities and the highestpriority is given to calls regarding downed power lines.

Utilities also receive substantial calls for downed power lines from thepublic that turn out to be other types of lines, such as communicationslines, that do not pose the same threat; however, a response is requiredfor all such calls. Crews are immediately dispatched to the affectedareas to determine if the downed lines are power lines and if they areenergized. If energized, the crew will cut power to the affected areauntil the lines can be safely restored. This response can drain autility's resources, particularly after a large event as they must tendto all calls for downed lines, regardless of whether the lines areenergized or not, before they can begin their damage assessment andrestoration process for restoring power to the community. Additionally,a first responder's ability to access areas with downed power lines ishampered until a utility crew can physically come to the site to verifythat any downed power lines are de-energized and the site is safe.

Thus, a need exists for a status indicator device for determining if adowned line is energized and relaying that status information to anelectric utility as well as anyone who may be in the vicinity of thedowned line. Ideally, the status indicator should be incorporated intohardware that is already present in a power distribution system, such asa power line “insulator.”

Overhead conductors for high-voltage electric power transmission arebare, and are insulated by the surrounding air. Conductors for lowervoltages in distribution may have some insulation but are often bare aswell. Supports called insulators are required at points where conductingwires are supported by utility poles or transmission towers. Insulatorsare also required where wires enter buildings or electrical devices,such as transformers or circuit breakers, to insulate the wire from thecase.

Insulators used for high-voltage power distribution are made from glass,porcelain, or composite polymer materials. Porcelain insulators are madefrom clay, quartz, or alumina and feldspar, and are covered with asmooth glaze to shed water. Insulators made from porcelain rich inalumina are used where high mechanical strength is a criterion.Porcelain has a dielectric strength of about 4-10 kV/mm. Glass has ahigher dielectric strength, but it attracts condensation and the thickirregular shapes needed for insulators are difficult to cast withoutinternal strains.

Recently, some electric utilities have begun converting to polymercomposite materials for some types of insulators. These are typicallycomposed of a central rod made of fibre reinforced plastic and an outerweathershed made of silicone rubber or ethylene propylene diene monomerrubber (“EPDM”). Composite insulators are less costly, lighter inweight, and have excellent hydrophobic capability. This combinationmakes them ideal for service in polluted areas.

The electrical breakdown of an insulator due to excessive voltage canoccur a puncture arc or a flashover. A puncture arc is a breakdown andconduction of the material of the insulator, causing an electric arcthrough the interior of the insulator. The heat resulting from the arcusually damages the insulator irreparably. Puncture voltage is thevoltage across the insulator that causes a puncture arc. A flashover arcis a breakdown and conduction of the air around or along the surface ofthe insulator, causing an arc along the outside of the insulator.Flashover voltage is the voltage that causes a flash-over arc. Most highvoltage insulators are designed with a lower flashover voltage thanpuncture voltage, so they flash over before they puncture, to avoiddamage.

Dirt, pollution, salt, and particularly water on the surface of a highvoltage insulator can create a conductive path across it, causingleakage currents and flashovers. The flashover voltage can be reduced bymore than 50% when the insulator is wet. High voltage insulators foroutdoor use are shaped to maximise the length of the leakage path alongthe surface from one end to the other, called the creepage length, tominimise these leakage currents. To accomplish this, the surface ismolded into a series of corrugations or concentric disc shapes. Theseusually include one or more sheds; downward facing cup-shaped surfacesthat act as umbrellas to ensure that the part of the surface leakagepath under the ‘cup’ stays dry in wet weather. Common insulator classesinclude: “pin type,” “suspension,” “strain,” “shackle,” “bushing,” “linepost,” “cut-out,” and “station post.”

The pin type insulator is mounted on a pin on the pole cross-arm ordirectly on the pole. There is a groove on the upper end of theinsulator. The conductor passes through this groove and is tied to theinsulator with annealed wire of the same material as the conductor. Pintype insulators are used for transmission and distribution of electricpower at voltages up to 33 kV. Beyond operating voltage of 33 kV, thepin type insulators become too bulky and hence uneconomical.

Higher voltage transmission lines usually use modular cap and pininsulator designs wherein wires are suspended from a “string” ofidentical disc-shaped insulators that attach to each other with metalclevis pin or ball and socket links. The advantage of this design isthat insulator strings with different breakdown voltages, for use withdifferent line voltages, can be constructed by using different numbersof the basic units. Also, if one of the insulator units in the stringbreaks, it can be replaced without discarding the entire string. Eachunit is constructed of a ceramic or glass disc with a metal cap and pincemented to opposite sides.

Ideally, a status indicator device should comprise a sensor node inconjunction with a visual or audio indicator. The device should capturethe status of a downed line, and if the line is energized, an alarm,message, or notification should be sent to the utility's operationscenter, in addition to providing an indication of hazardous conditionsto anyone in the vicinity of the downed line. If the downed line is notenergized, the device must still provide a status both to the utilityand to anyone in the vicinity. Additionally, as previously stated, astatus indicator device should be incorporated into pre-existing systemhardware, such as a power line “insulator.” However, the known prior artdevices (described below) fail to meet these needs.

U.S. Pat. No. 5,414,344 discloses an e-field sensing apparatus thatdetects the energization of high voltage utility transmission anddistribution lines. An external housing substantially shields internalcomponents of the apparatus from the detected E-field. A conductive wireextends from the housing where it is exposed to the E-field. A signal isinduced onto the exposed wire and sensed by the apparatus. The length ofexposed wire and the distance of the apparatus from the high voltageline attenuate the E-field so the induced signal is within operationalparameters of internal sensing components. Adjustments to the wirelength and apparatus distance enable detection of E-fields surroundingpower lines carrying voltage levels of a predetermined voltage level(i.e. approximately 2000 volts and higher). In response to the E-field,the apparatus generates an analog output signal and a line isolationcontrol (one-bit digital) signal. The analog output signal drives ameter, LED or other indicating device serving to aid maintenanceengineers. The analog output also provides data to a SCADA or othercontrol/indication system. The control signal drives a relay to anormally open position or trips the relay closed when the line powerfails. The control drives motors to either maintain or isolate (shutdown) power lines at a power substation.

U.S. Pat. No. 5,550,751 discloses a method and apparatus for detectinghigh impedance faults occurring on a distribution circuit coupled to anAC power source. Weighted multiple technique outputs are combined todetermine whether a high impedance fault has occurred.

U.S. Pat. No. 5,706,354 discloses a device is connected in a signal pathfor canceling an unwanted noise signal induced by and correlated to theAC power line. The noise signal is assumed to have relatively constantphase (with respect to the AC power line) and amplitude during theperiod of use. The desired signal is assumed to be temporarily mutablefor a brief period during which the noise signal is acquired. Amanually- or automatically-adjusted gain (or attenuation) stage andoverload detector are at the front-end of the waveformacquisition/playback block. A manually- or automatically-adjusted stage,typically linked to the earlier gain (attenuation) stage and withcomplementary attenuation (or gain) is at the back-end of the waveformacquisition/playback block. In this way, maximum performance can berealized from a waveform acquisition/playback block of lower resolutionover a wide range of noise signal levels. The device acquires N samplesof the noise signal over one or more periods of the AC power cycle andin synchrony with the AC power cycle. The sampling is terminated and thestored signals are played back with the correct amplitude and summed 180degrees out-of-phase with the original noise signal.

U.S. Pat. No. 6,002,260 discloses a fault sensor suitable for use in aheterogenous power distribution system executes a stored program andcauses sufficient information to be collected to distinguish a source offault current as being from a public utility portion of the powerdistribution network or from a distributed generator. Short circuitcurrent and magnetizing current are reliably distinguished based ondifferences in VI “signatures.” In addition, the fault sensorperiodically senses a condition of a battery of the fault sensor. Whenthe condition of the battery indicates the battery power is low, thefault sensor sends a digital data signal including a low batteryindication to a remote location. Subsequent to occurrence of a sustainedpower outage, the sensor detects that power has been restored and sendsto a remote location a digital data signal including an indication thatpower has been restored. The sensor periodically measures peak linevoltage and peak line current and reports peak values to the remotelocation.

U.S. Pat. No. 6,128,204 discloses a line power unit controls electricalpower delivery to a grid from a three phase permanent magnet generator.A line power unit controller receives a power level command and controlsa main inverter that draws DC power from a DC bus to deliver thecommanded power to a grid. The DC bus is fed DC voltage via a threephase permanent magnet generator and a rectifier. The inverter deliverspower to the grid via a filter, transformer and main contactor. The linepower unit controller also controls the main contactor to break theconnection with the grid. A precharge circuit draws power from the gridto precharge the DC bus to a precharge voltage. Alternatives include astart inverter separate from the main inverter that permits simultaneousdelivery of power to the grid and commutation of the permanent magnetgenerator as a motor to spin an engine connected thereto at a speedsufficient to permit engine starting. Another alternative utilizes asingle inverter for engine starting and power delivery which does notpermit these operations to be simultaneously performed. Furtheralternatives include eliminating the transformer by utilizing ahigh-voltage rated main inverter.

U.S. Pat. No. 6,445,196 discloses a transformer test control devicepermits testing of an electrical transformer as installed on a powerpole without connecting any high voltage of the power distribution lineto the transformer. The test control device combines a visual indicatoracting as both a power-on indicator and a fuse tester, a voltmeter, avoltage adjustment control, an operator control switch and a fuse aswell as terminals for connecting both to an alternating currentelectrical supply and to the terminals of the primary coil of atransformer to be tested. Additionally, the test control device includesterminals for connecting the device and a secondary circuit to selectedoutput terminals of the secondary coil of the transformer and additionalterminals for receiving and retaining the contact portions of voltmetertest probes. This device may be embodied to include a dedicated secondvoltmeter. The test control device may be powered by either normal 120volt line voltage or the output of a power inverter connected to theelectrical system of a truck or other motor vehicle in those areaswithout readily available 120 volt AC power.

U.S. Pat. No. 6,459,998 discloses a system by which a “downed” powerline is detected by sensing whether there is an open circuit along thepower line and producing an indication that an open circuit conditionexists. In response to an indication that an open circuit conditionexists, the system compares the nature of the voltage and/or currentsignals present on the power line at the time an open circuit conditionis indicated to exist, with a preprogrammed stored condition whichincludes typical signals to be expected when a “break” occurs along apower line. When a downed power line is detected, power is then removedfrom the affected line.

U.S. Pat. No. 6,549,120 discloses a powerline communication systemincluding a transmitter having a pair of terminals for connection to thepower lines. The transmitter comprises a carrier frequency generator forgenerating a carrier frequency modulated by the data signal and aswitching circuit connected to the carrier frequency generator for beingswitched by the carrier frequency generator for generating a carriersignal having the carrier frequency. The switching circuit is connectedto the terminals for providing the generated carrier signal thereto. Theswitching circuit comprises at least one storage means for storingenergy when generating a portion of a cycle of the carrier signal andproviding the stored energy when generating another portion of the cycleof the carrier signal. The system also comprises a receiver coupled tothe power lines. The receiver includes a filter means for filtering thecarrier signal from the power line signal and a demodulator connected tothe filter means for extracting the data signal from the carrier signal.Both the transmitter and receiver may utilize a digital algorithm in acomputing device to synchronize the carrier signal to the power linefrequency to adaptively track changes in the power line frequency tominimize interference with power line harmonics and provide accuratefrequency alignment between the transmitter and receiver.

U.S. Pat. No. 6,829,724 discloses a method for battery conditiontesting. In one embodiment, the method is comprised of interrupting ACpower service to a data storage system. The interruption causes anexhaustible power source to provide operating power to the data storagesystem. The exhaustible power source is coupled to said data storagesystem. The exhaustible power source is adapted to provide operatingpower to the data storage system when the AC power service to the datastorage system is interrupted. The method is further comprised ofdischarging the exhaustible power source by operating the data storagesystem with the exhaustible power source for a specified period of timeless than full discharge but sufficient to fully flush the cache. Theexhaustible power source passes the condition testing provided theexhaustible power source provides operating power to the data storagesystem for the specified period of time. The method is further comprisedof recharging the exhaustible power source subsequent to the exhaustiblepower source passing the condition testing.

U.S. Pat. No. 6,879,479 discloses an apparatus for sensing and measuringthe HV surge arrester current includes two toroidal current transformersarranged coaxially with respect to the earth wire of the surge arrester,elements for sensing the current signals emitted by the transformers andfor converting the current signals in digital signals, and elements fortransmitting the digital signals to an information network and analogstate signals by relay activation. The two toroidal current instrumenttransformers are associated, respectively, one to elements for sensingthe normal leakage current, and the other to elements for sensing theimpulsive current, the latter comprising a circuit (TRIGGER)discriminating between “switching” and “lightning” signals, in which thebasis for discrimination is a signal duration threshold, of about 35 ps.

U.S. Pat. No. 6,914,763 discloses a utility power distribution systemhaving at least one primary electric power source and at least onesecondary electric power source, each of said primary and secondarysources being connected to the distribution system through respectivecontrollable circuit breakers, further comprising communication signalgenerating apparatus arranged for introducing a communication signalinto the power distribution system from the connection of the primarypower source, communication signal receiving apparatus arranged forreceiving the communication signal via the power distribution system atthe secondary power source, and apparatus responsive to the interruptionof receipt of the communication signal at the receiving apparatus foroperating the circuit breakers at the secondary power source fordisconnecting the secondary power source from the power distributionsystem.

U.S. Pat. No. 7,076,378 discloses an apparatus for determining acharacteristic of a portion of a power line. The apparatus comprises acoupling device in communication with a processor. The coupling devicereceives a signal from a power line and the processor receives thesignal from the coupling device and determines a characteristic of aportion of the power line based on the received signal.

U.S. Pat. No. 7,113,134 discloses an antenna device, system and methodof installing the antenna device for receiving a wireless signal at apad mounted electrical transformer. The device includes an antennacapable of communicating the wireless signal and a material locatedaround the antenna. The material facilitates attachment to the padmounted electrical transformer as well as preventing access to theantenna. The antenna may be covered by or embedded within the material.The material may be emissive and/or insulative. In addition, the devicemay include a conductor that passes through an enclosure of the padmounted transformer. The conductor may be communicatively coupled to afirst communication device that provides communication to a customerpremise that is electrically coupled to the pad mounted electricaltransformer.

U.S. Pat. No. 7,248,158 discloses an automated meter reading power linecommunications system which may include measuring the utility usage of afirst customer premises to provide first utility usage data, storing thefirst utility usage data in memory of a first device, wirelesslytransmitting the first utility usage data from the first device,receiving the wirelessly transmitted first utility usage data at asecond device coupled to a medium voltage power line, and transmittingthe first utility usage data over the medium voltage power line.

U.S. Pat. No. 7,436,321 discloses a method of communicating utilityusage data is provided. In one embodiment, the method comprisingtransmitting real-time utility usage data from a plurality of utilitymeters, receiving the real-time utility usage data from the plurality ofutility meters, storing the real-time utility usage data in a memory,storing address information of the plurality of utility meters inmemory, receiving requests from a plurality of utility users forreal-time utility usage information and wherein the requests traverse acommunication path that includes the Internet, processing the utilityusage data of the utility users to provide the real-time utility usageinformation for each utility user, and transmitting the real-timeutility usage information to the utility users over a communication paththat includes the Internet.

U.S. Pat. No. 7,453,352 discloses transmitting data signals between apower line and a computer, wherein the power line provides power to thecomputer via a distribution transformer and the computer is incommunication with a wireless communication path. A first data signal iscommunicated with the power line. A conversion is made between the firstdata signal and a second data signal capable of being communicatedwirelessly. The second data signal is wirelessly communicated with thewireless communication path.

U.S. Pat. No. 7,626,489 discloses a power line communication systemnetwork element that provides communications to one or more userdevices. The device may also receive data from one or more sensors, suchas current sensors, a voltage sensor, a video camera, a temperaturesensor, a barometer, a motion sensor, a level sensor, and/or a vibrationsensor. The device may include a controller that receives commands thatrelate to the collection and transmission of the sensed data via amedium voltage power line.

U.S. Pat. No. 7,701,325 discloses communication device for use with apower line communication system. One embodiment forms a bypass deviceand comprises a LV coupler, a LV signal conditioner, a controller, a MVmodem, a first MV signal conditioner, an isolator, a second MV signalconditioner, and a MV coupler. The controller may provide routingfunctions to give priority to certain types of data, control access tothe network, filter data packets, process software upgrades, andprovision new subscriber devices. In addition, the controller maymonitor, process, and transmit traffic data, measured power data,errors, and other collected data.

U.S. Pat. No. 7,705,747 discloses a sensor network for monitoringutility power lines comprises a sensor disposed for monitoring utilitypower lines, the sensor capable of acquiring data related to the utilitypower lines and communicating sensor data; a first remote sensorinterface (RSI) comprising a data communications device capable ofreceiving the sensor data communicated from the sensor, and transmittingdata relating to the received sensor data; and a data communicationsdevice capable of receiving the data transmitted by the first RSI andtransmitting data related to the sensor data directly or indirectly to anetwork external to the sensor network. The sensor network comprises acommon designation network.

U.S. Pat. No. 7,714,592 discloses a system and method of detectingchanges in the impedance of a segment of medium voltage power line isprovided. In one embodiment, the method comprises receiving voltage datacomprising data of the voltage of the power lines at locations at aplurality of different points in time, receiving current data thatcomprises data of the current flowing between adjacent locations at theplurality of points in time, intermittently determining an impedance ofthe power lines between adjacent locations based on the voltage data andcurrent data, monitoring the impedance of the power lines betweenadjacent locations over time, and providing a notification of a changein the impedance of a power line between adjacent locations upondetection of a change in the impedance beyond a threshold change.

U.S. Pat. No. 8,077,049 discloses a system, device, and method ofproviding information for a power distribution system is provided. Inone embodiment, a method of using a device that receives power from thelow voltage power of the power distribution system and experiences apower loss during a local power outage may perform the processes ofmonitoring a voltage of the low voltage power line, detecting a voltagereduction below a threshold voltage for a predetermined time period,storing information of the voltage reduction in a non-volatile memoryprior to the power outage, and transmitting a notification to a remotecomputer system prior to the outage. The monitoring may comprise makinga plurality of measurements of the voltage during a time interval andaveraging the plurality of voltage measurements. In addition, the methodmay include transmitting an alert message upon power up after the outageto indicate a power restoration local to the device.

U.S. Pat. No. 8,336,352 discloses a transient detector and faultclassification system comprising an algorithm that detects transientswhich may result from the occurrence of a fault in the powerdistribution system. The system includes a detection module whichprocesses a set samples obtained from electrical waveforms propagated ofthrough the power distribution system and appear to be statisticallyanomalous compared to other sample data. This is done using an adaptivedetection algorithm that is applied when large changes occur in awaveform over a relatively short period of time. The identified samplesare then provided to a signal classifier module which processes sets ofsamples to classify a transient they represent as a likely faultoccurrence or some other type of anomaly which is likely not a faultoccurrence. If a transient is classified as representing a likely faultoccurrence, a polling module polls users of the distribution system todetermine if a fault has occurred within the distribution system, and,if so, where.

U.S. Pat. No. 8,509,953 discloses a smart grid for improving themanagement of a power utility grid is provided. The smart grid includesusing sensors in various portions of the power utility grid, usingcommunications and computing technology, such as additional busstructures, to upgrade an electric power grid so that it can operatemore efficiently and reliably and support additional services toconsumers. Specifically, the additional bus structures may comprisemultiple buses dedicated to the different types of data, such asoperational/non-operational data, event processing data, gridconnectivity data, and network location data. The multiple buses maycomprise different segments in a single bus or may comprise separatebuses. The multiple buses may be used to transport the various types ofdata to other smart grid processes (such as at a centrally locatedcontroller).

U.S. Pat. No. 8,674,843 discloses a system and a method for detectingand localizing abnormal conditions and electrical faults in anelectrical grid are provided. A method includes receiving a notificationmessage including a state of an electrical component on an electricalgrid. The method further includes displaying, by a computing system, analarm message indicating the state of the electrical component to asystem operator responsible for the electrical component such thatsystem operator is able to determine at least one action to take inresponse to the state of the electrical component.

U.S. Pat. No. 8,779,931 discloses a system, device, and method ofproviding information for a power distribution system is provided. Inone embodiment, a method of using a device that receives power from thelow voltage power of the power distribution system and experiences apower loss during a local power outage may perform the processes ofmonitoring a voltage of the low voltage power line, detecting a voltagereduction below a threshold voltage for a predetermined time period,storing information of the voltage reduction in a non-volatile memoryprior to the power outage, and transmitting a notification to a remotecomputer system prior to the outage. The monitoring may comprise makinga plurality of measurements of the voltage during a time interval andaveraging the plurality of voltage measurements. In addition, the methodmay include transmitting an alert message upon power up after the outageto indicate a power restoration local to the device.

U.S. Pat. No. 8,810,421 discloses a system, computer program product andmethod to provide information related to a power distribution systembased on information provided by a plurality of network elementselectrically connected to a plurality of power lines of the powerdistribution system at a plurality of locations is provided. In oneembodiment, the method comprises receiving a notification from a groupof network elements that have detected a voltage signature indicating animminent power outage, determining location information of the poweroutage, outputting the location information of the power outage,receiving a live notification from a first network element of the groupof network elements indicating a first power restoration at a locationof the first network element, determining location information of thefirst power restoration, and outputting the location information of thefirst power restoration.

Thus, it is an object of the present invention to provide a downed powerline sensor contained in a single package that also performs thefunction of the insulator. It is a further object of the presentinvention to provide a drop-in replacement for current power linepin-type insulators, allowing it to be easily incorporated into the gridwithout changes in the methodology of grid construction. It is a furtherobject of the present invention that the sensor can be installed on autility pole or cross arm using existing methods and techniques, thatthe senor does not have any external wiring or other mechanicalconnections. The sensor operates off of battery power so that it canfunction in the absence of line power. When current is flowing on theline, the battery is charged by an energy harvesting componentincorporated into the sensor.

It is a further object of the present invention to measure line currentand voltage. Whether or not a power line is downed cannot be identifiedwith certainty by only measuring line current and voltage. Therefore, toovercome that uncertainty, in addition to measuring the current andvoltage on the power line, it is an object of the present invention tomeasure the tension in the power line, enabling the system to indicate apower line is down or in contact with an object.

SUMMARY

A wireless sensor apparatus for determining and reporting the status ofan electrical wire, said sensor apparatus comprising: an electricallyinsulated housing; a non-contact electrical energy harvesting device,said energy harvest device disposed within said housing, said energyharvesting device comprising an electric current detector and voltagedetector; an electric power source, said power source operativelyconnected to said energy harvesting device; a microcontroller, saidmicrocontroller operably connected to said power source; a mechanicallyrigid base, said base operably connected to said housing and to said atleast one strain gauge, said at least one strain gauge operablyconnected to said power source and to said microcontroller; a wirelessdata transmission antenna, said wireless data transmission antennaoperably connected to said power source and to said microcontroller; avisual display, said visual display operably connected to said powersource and to said microcontroller.

A wireless sensor apparatus for determining and reporting status of anelectrical wire, said sensor apparatus physically disposed in contactwith said wire and comprising: an electrically insulated housing; ameans for wireless electrical energy harvesting, said means for wirelesselectrical energy harvesting disposed within said housing; a means forproviding electrical power to said sensor apparatus, said means forproviding electrical power operatively connected to said energyharvesting device; a microcontroller, said microcontroller operablyconnected to said apparatus; a means for measuring the mechanical loadon said housing, said means for measuring the mechanical load on saidhousing operably connected to said microcontroller; a means fordetermining the presence of an electric current through said electricalwire, said means for determining the presence of an electric currentthrough said electrical wire operably connected to said microcontroller;a means for determining the presence of an electric voltage within saidelectrical wire, said means for determining the presence of an electricvoltage operably connected to said microcontroller; a means for wirelessdata transmission, said means for wireless data transmission operablyconnected to said microcontroller; a visual display, said visual displayoperably connected to said microprocessor.

A method of sensing and reporting the mechanical and electrical statusof a power line, said method comprising the steps of: providing asensor, where said sensor harvests power from a proximate power line;using said sensor to detect the current in an proximate power line;using said sensor to detect the presence of a voltage in said powerline; using said sensor to detect the mechanical load on said powerline; using said sensor to communicate the mechanical and electricstatus of said power line to a system user.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription given hereinafter and from the accompanying drawings of thepreferred embodiment of the present invention, which, however, shouldnot be taken to limit the invention, but are for explanation andunderstanding only.

In the drawings:

FIG. 1 shows a side elevation view of a prior art pin type insulator.

FIG. 2 shows a cross sectional view of the prior art insulator of FIG.1.

FIG. 3 shows a side cross sectional view of an exemplary embodiment of apower line status sensor according to the present invention.

FIG. 4 shows a top view of the power line status sensor of FIG. 3.

FIG. 5 shows a side cross-sectional view of an alternative exemplaryembodiment of a power line status sensor according to the presentinvention.

FIG. 6 shows an exploded side assembly view of the status sensor of FIG.5.

FIG. 7 shows a block diagram of the control logic for the load sensingaspect of an exemplary embodiment of a power line status sensoraccording to the present invention.

FIG. 8 shows a block diagram of the overall control logic of anexemplary embodiment of a power line status sensor according to thepresent invention.

FIG. 9 shows a functional schematic diagram of an energy harvester foruse in an exemplary embodiment of a power line status sensor accordingto the present invention.

FIG. 10 shows a perspective side view of a power line status sensoraccording to the present invention, where said sensor is installed on apower line.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention will be discussed hereinafter in detail in termsof various exemplary embodiments according to the present invention withreference to the accompanying drawings. In the following detaileddescription, numerous specific details are set forth in order to providea thorough understanding of the present invention. It will be obvious,however, to those skilled in the art that the present invention may bepracticed without these specific details. In other instances, well-knownstructures are not shown in detail in order to avoid unnecessaryobscuring of the present invention.

The following detailed description is merely exemplary in nature and isnot intended to limit the described embodiments or the application anduses of the described embodiments. As used herein, the word “exemplary”or “illustrative” means “serving as an example, instance, orillustration.” Any implementation described herein as “exemplary” or“illustrative” is not necessarily to be construed as preferred oradvantageous over other implementations.

All of the implementations described below are exemplary implementationsprovided to enable persons skilled in the art to make or use theembodiments of the disclosure and are not intended to limit the scope ofthe disclosure, which is defined by the claims. In the presentdescription, the terms “upper”, “lower”, “left”, “rear”, “right”,“front”, “vertical”, “horizontal”, and derivatives thereof shall relateto the invention as oriented in FIG. 1.

Furthermore, there is no intention to be bound by any expressed orimplied theory presented in the preceding technical field, background,brief summary or the following detailed description. It is also to beunderstood that the specific devices and processes illustrated in theattached drawings, and described in the following specification, aresimply exemplary embodiments of the inventive concepts defined in theappended claims. Hence, specific dimensions and other physicalcharacteristics relating to the embodiments disclosed herein are not tobe considered as limiting, unless the claims expressly state otherwise.

As described above, prior art downed power line sensors attempt todetermine whether a power line is down and energized based solely onalgorithms using only the inputs of current and voltage. However, theseinputs alone are unlikely to reliably and accurately indicate the statusof a power line. For example, current and voltage may be absent evenwhen the power line is still mechanically sound.

The system of the present invention, however, adds another input,tension on the line, to monitor whether the mechanical load on the powerline has changed. Used together, information based on all three types ofinputs: current, voltage, and tension, provides a dependable indicationof the “status” of a powerline. The status of a powerline, includeswhether the powerline is physically in good condition and whether apower line is energized.

Referring first to FIG. 1, there is shown a prior art pin-type insulatorfor use in conjunction with overhead utility power lines. FIG. 2 furtherillustrates a cross-sectional view of the pin-type insulator shown inFIG. 1. As illustrated in FIGS. 1 and 2, prior art insulators generallycomprise a housing comprising a non electrically conducted material suchas high density polyethylene (“HDPE”). The housing is disposed about atop end of a metal post as shown in FIG. 2. In the side elevational viewand side cross sectional views shown in FIGS. 1 and 2, respectively, thehousing of the prior art insulator is generally symmetric about itsvertical axis. The prior art insulator housing further comprises aplurality of rings vertically offset from one another and extending fromthe center of the housing. The rings taper distally from the center ofthe housing.

The apparatus of the present invention, has been conceived of to replaceprior art pin-type insulators, illustrated in FIG. 1 and in FIG. 2, andcurrently in use on utility poles or cross-arms with a downed power linesensor according to the present invention.

Referring now to FIG. 3, downed power line sensor 1000 of the presentinvention generally comprises insulator housing 100. Insulator 100 ispreferably a single molded piece generally comprising a non electricallyconductive material such as HDPE and generally cylindrical cavityaccessible from the bottom such that insulator housing 100 can bedisposed over non-contact energy harvester 200; adapter plug 300; loadcell post 400; rechargeable batteries 500; LEDs 600; system controller700; communications module 800; and RF antenna 900.

Referring still to FIG. 3, communication module 800 further comprises asingle donut shaped circuit card containing a microprocessor, load cellelectronics, and a battery charger, connected to rechargeable batteries500. Module 800 controls all electrical functions within downed powerline sensor 1000. It distributes power to the other elements, monitorsthe load cell, controls the system logic, sends status to the visualstatus indicator, and sends alerts to the communications module.

Communications module 800 is further operatively connected to radiofrequency (“RF”) antenna 900 for wireless communication of a powerline's status (energized, non energized, in place, fallen, etc.) with asystem provider such as a utility company or a government, military, orlocal safety agency, such as a police or fire department. Communicationsmodule 800 is further operatively connected to system controller 900.The system controller circuit card of controller 900 will be designedand built around a microcontroller or equivalent that provides the logicwhich defines the system functionality. An electrical block diagram ofthe system controller circuit card of sensor 1000 electronics is shownin FIG. 8.

Referring still to FIG. 3, insulator housing 100 of downed power linesensor 1000 comprises collinear cavities in which non-contact energyharvester 200 is electronically connected to batteries 300 is disposed.The subassembly of energy harvesters 200 and rechargeable batteries 300is placed atop and operably connected to system controller 700,communications module 800, and RF antenna 900. Referring still to FIG.3, downed power line sensor 1000, further comprises a load cell post 400and an adaptor plug 300 for operably attaching energy harvester 200.

Referring still to FIG. 3, sensor 1000 further comprises at least oneLED 600 operably connected to system controller 700 and rechargeablebatteries 500. Controller 700 instructs LEDs 600 to flash or other wirefunction to display power line status information. FIG. 4 shows a topview of system controller 700. As illustrated FIG. 4, controller 700preferably comprises a plurality of LEDs 600 disposed around thecircumference of sensor 1000.

Shown in FIG. 10, a utility power line is attached to the top of sensor1000 using the same techniques as a standard insulator. The closeproximity of the conductor with the sensor permits an energy harvestingsystem to charge a battery which will power the sensor 1000. In thepreferred embodiment of the present invention, the energy harvestingsystem comprises alternating electrical energy harvesters 200.

Alternating current (“AC”) energy scavenging for electric power systemsensing is presently implemented using coil-based approaches. Coil-basedenergy scavengers can be categorized as current transformers, fluxconcentrators, or Rogowski coils. Current transformers are by far themost common coil-based AC scavenging method. A current transformer'score can be either continuous, and the conductor has to be disconnectedfor installation, or split and the scavenger is installed around theconductor. The degradation of the gap over time in a split core currenttransformers may cause leakage of the magnetic flux, and causecalibration problems if the scavenger is also used as a current sensor.When the current-carrying conductor cannot be fully encircled by the ACscavenger, such as in the case of “stickon” sensors, a flux concentratorwith a core that only partially encircles the conductor can be used. Themagnetic coupling in this type of energy scavenger is drasticallyreduced compared to a current transformer due to increased reluctance ofthe magnetic circuit (most of the flux must now travel through air). ARogowski coil corresponds essentially to a current transformer with anair-core, and is frequently used for current sensing application.Although the coil surrounds the conductor, the lack of a rigid corefacilitates the installation. However, a Rogowski coil is generally notused as a current scavenger due to its low coupling efficiency.

Energy harvesters 200, however, preferably instead comprise permanentmagnets attached to a piezoelectric beam in the electric fieldsurrounding the conductor will cause the magnets to oscillate at thesame frequency as the alternating current in the power line. Thisoscillation causes a deflection in the piezoelectric beam, creatingpower that can be harvested to charge the battery powering the sensor.There is no electrical contact with the utility power line and there issufficient insulating material between the magnets and the power line toallow the sensor to be a fully functional insulator. This energyharvesting technology is fully described in Igor Paproiny, et al.,Electromechanical Energy Scavenging from Current-Carrying Conductors(IEEE Sensors Journal 2011 and Qiliang Richard X U, et al., MiniatureSelf-Powered Stick-On Wireless Sensor Node for Monitoring Overhead PowerLines (Berkeley Sensor and Actuator Center). The entire disclosure ofthese papers is hereby incorporated herein by reference.

Thus, as illustrated in FIG. 8, energy harvesters 200 of the presentsensor 1000 comprise electromechanical AC energy scavenging devices thatuse permanent magnets to couple an electromechanical resonator to thecurrent flowing in a nearby conductor. The alternating magnetic fieldexcites the magnets, which constitute the proof mass of the mechanicalresonator. The resulting strong coupling combined with resonance atstandard electrical power frequencies (e.g. 50 Hz or 60 Hz) enables thescavenger to generate more power than can be obtained by usingcomparable coil-based approaches. Alternatively, energy harvester 200may comprise a vibrational energy scavenging device. In any case,however, energy harvester 200, further comprises voltage and currentdetectors (not shown) of known design. In the absence of current flow,energy harvester 200 still detects voltage in the electric fieldsurrounding the power line.

Referring to FIG. 9, electromechanical AC energy harvester 200 generallycomprises a permanent magnet which also doubles as the proof-mass, aspring with stiffness k, mechanical, and electrical damping.Electromechanical AC energy scavenging is similar in principle toelectro-dynamic wireless power transfer, however the present device usespiezoelectric (as opposed to electromagnetic) coupling to convert theenergy from the mechanical domain.

Again referring to FIG. 9, the general model of electromechanical ACenergy harvester 200 comprises an underdamped 2nd order resonatingmass-spring system. The moving mass is subject to mechanical damping,while the output energy of the scavenger is extracted through atransducer (a piezoelectric cantilever), and corresponds to theelectrical damping.

In contrast to vibrational energy scavenging, electromechanical ACenergy scavenging uses permanent magnets as the resonating mass. Thesemagnets are excited by the force from the alternating magnetic fieldgenerated by the current in a nearby conductor. If the frequency offorce matches the resonant frequency of the electromechanical system,the amplitude of the displacement of the mass, and correspondingly theoutput power, is maximized. A stopper spring limits the motion of themagnetic mass (and prevent the generation of excessive stresses in thepiezoelectric layer) during large excitations.

Energy harvester 200, further comprises voltage and current detectors(not shown) of known design. If energy harvester 200 is collecting powerline is harvesting power. In the absence of current flow, energyharvester 200, still detect current voltage in the electric fieldsurrounding the power line.

Referring again to FIG. 3 or to the alternative embodiment of FIG. 4,sensor 1000 further comprises a load cell post 400 upon which theelectronics of sensor 1000 are disposed. Load cell post 400 comprisesstrain gauges (not shown) to monitor the mechanical load on post 400.The strain gauges are connected electronically to sensor 1000 capable ofmeasuring the forces acting on load cell post 400.

Strain gauges are used to measure force or weight. Because itselectrical resistance varies as it is stretched or compressed, a straingauge measures elongation or compression on the surface to which it ismounted. Using the strain gauge measurement and the mechanicalproperties of post 400, any forces on post 400 can be determined.

The load cell strain gauges are preferably configured in a Wheatstonebridge configuration. This configuration provides the ability to balancethe circuit and compensate for changes in temperature. An amplificationcircuit connected to the Wheatstone bridge amplifies the output signalfrom the Wheatstone bridge to increase measurement resolution andimprove the signal to noise ratio.

The configuration of load cell post 400 is preferably designed to meetthe needs for the targeted range of utility line conductor sizes. Forexample, standard wire sizes may be 556, 4/0, and 2/0 AAC or 477, 3/0,and #2 ACSR. Conductors may have a design line tension of 8003,600pounds. If a line with these tensions was to be severed and the fullline tension placed on the load cell, the strain exerted on load cellpost 400 will be well within the capabilities of the strain gauges.

The base of the load cell post 400 further comprises mounting bolt 500necessary to attach the complete sensor to the utility pole orcross-arm. Based on the pin type insulator hardware currently used,sensor 100 will be robust and at least as structurally strong as theinsulators it will replace. To quantify the tension variations, the loadcell strain gauges measurements need to be electrically amplified andmanipulated. The circuitry required for this is included in electronicmodule 800 and controller 700 of sensor 1000.

As shown in FIG. 7, a moving average filter is applied by electronicmodule 300 to the strain gauge measurements. This design prevents falsepositives due to phenomena such as galloping of the line and otherintermittent line movements. The resulting measurements can then becompared to established limits to further prevent false positives andcreate the downed line alert message.

The present invention may further comprise an accelerometer to identifyinstances of sudden mechanical failure in a power line. If the tensionevent breaks the utility pole cross arm, the accelerometer will sensethat movement. This information will be included in the alert message totell the user that the damage to the pole is more significant andadditional crew may be needed.

To work within the power budget, the load cell preferably operates on a1-second duty cycle. However, those of skill in the art will appreciatethat the duty cycle may be adjusted to match capability of the energyharvester. For example, the power budget may place the load cellcontroller on a 10% duty cycle, and the strain gauge excitation on a 20%duty cycle, allowing time in each 1-second cycle for the gauges tothermally stabilize before the measurement is taken, increasing the loadcell accuracy.

Most of the Wheatstone bridge excitation and measurement can be handledby standard integrated circuit chips. Each branch of the Wheatstonebridge may, for example, have nominal resistance of 1000 Ohms, so theexcitation current supplied to the load cell is 3 mA and the excitationpower is 9 mW.

Referring now to FIG. 10, sensor 1000 monitors the differential forcebetween the line tension in both directions along the axis of the powerline. When the sensor is initially installed and the line powered, abaseline will be electronically established. This baseline will haveapproximately the same tension in the line in both directions. In theevent that a line is taken down, the tension in that span will decrease,causing an increase in strain in the load cell.

As illustrated in FIG. 10, sensor 1000 is attached to a power line ofinterest. Tension in the power line is monitored by measuring the loadon post 400 of the sensor 1000 which is physically connected toinsulator housing 100. Thus, changes in the tension on the power linewill cause minute deflections in load cell post 400, which the straingauges detect.

When approximately equal forces are applied to the sensor load cell viathe power line attached to insulator 100, the load cell post is in anapproximately neutral state, where the outer surface is in neithercompression nor tension, as represented by the center image of FIG. 10.If the line on one side of the sensor 1000 is broken, the tensiondecreases in the direction of the break and increases in the oppositedirection as represented by the right image of FIG. 10.

Conversely, if a fallen tree or other object is contacting the line, itincreases the tension in that section of line and the load on load cellpost 400.

Downed power line sensor 1000 of the present invention ideally provides“real time” information about the mechanical (downed line) andelectrical (energy state) status of a power line to the system user,which may be a government agency, a utility provider, the military, orpublic safety agency, such as the police or fire department. Toaccomplish this, power line status sensor 1000 further comprises antenna900 functionally connected to communications module 800 as shown inFIGS. 3 and 4. Information about the status of a power line collected bysensor 1000 can then be sent to the system user via a wirelesscommunications network.

Additionally, power line sensor 1000 preferably includes an indicator,such as LEDs 600, that provide information to first responders andothers at the scene regarding whether a downed power line is energized.

When the Downed Power Line Sensor is installed and the line is initiallyenergized, the sensor establishes the baseline condition for the loadcell. In the event of a downed power line, because the sensor ismonitoring current and voltage on the line, it can generate an alertthat a power line has experienced a tension event and indicates whetherthe line is energized. An energized state exists where either current orvoltage is present. An alert may will be displayed on a visual indicatoror sent to a remote utility service provider or other system user via awireless communications network.

In a preferred embodiment, the visual status indicator in sensor 1000consists of multicolored high output LEDs 600 equally spaced around theoutside of the electronics board. Each of LEDs 600 has an adequate,preferably 120 degree, viewing angle so when they are placed around theedge of the board, the viewing angle of adjacent LEDs 600 will overlap,ensuring that LEDs 600 are visible in any direction around the sensor.The visual indicator on sensor 1000 enables first responders orrestoration workers on scene to determine the status of the sensor andof the downed line.

LEDs 600 are able to illuminate in red, blue, and green light. While thepreferred power budget is based on an appropriate blink sequence once aminute, stored energy will be available to increase that rate asdesired. When sensor 1000 is functioning normally, LED 600 will flash adesired color light for predetermined intervals. This enables firstresponders on scene to know the sensor is functioning. When a line isdowned, sensor 1000 can have a set number, preferably 3, of consecutiveblinks in either red or green. Sensor 1000 will preferably cause LEDs600 to flash a green light when the power line is down and the line isnot energized and a red light when the power line is down but energized.Sensor 1000 may further comprise an audio indicator if a tension orenergy event occurs.

By flashing LEDs 600, it is easier to see in daylight. To increasedaytime visibility, an additional dark surface can be placed around eachLED 600 to increase the contrast. Sensor 1000 may further comprise areflective surface around LEDs 600 to further increase the daytimevisibility of the same.

A passive mechanical status indicator may be used to indicate the alertstatus of the sensor. However, if the sensor was to fail or be damagedwith the passive indicator in the “safe” display mode and the line wasactually energized, the sensor would wrongly indicate a non-energizedline and create a significant safety hazard. Thus, it is preferred thatthe visual indicator incorporate an active an active flashing LED 600,so that first responders on scene can know with certainty that thesensor is functioning properly.

The power required for the continuously operating a blue flashing LED600 is minimal and does not have a significant impact on the overallpower required by the sensor. Each LED 600 has a current draw and asupply voltage. This power will be supplied by the sensor battery, whichis charged by the energy harvester. In the event of a downed power line,the stored energy will allow the LEDs 600 to flash red or green threeconsecutive H second blinks, once every minute, for a minimum of 168hours (1 week), based on a power usage of 3.2 mW. However, the batteryhas excess capacity so alternative flash patterns can be explored if sodesired.

In the preferred embodiment of the present invention, at all times whenthe sensor is functioning and monitoring the power line status, an LEDvisual status indicator will flash. When a tension event has occurred,the LED will flash different colors at different intervals. For example,red may indicate the line is energized, and green may indicate it is notenergized. The blink pattern time, interval, and duration can bemodified as desired because there is ample power capacity in thebattery. The system may further compromise a manual or automatic resetswitch.

As previously stated, sensor 1000 further comprises means fortransmitting status information about the power line to remote systemusers, such as utility companies. However, most such potential systemusers have an existing version of network communications. For example,each electric utility has its own network communication system for smartmetering and other grid monitoring. Thus, sensor 1000 of the presentinvention comprises adequate power, signal input, and antenna access tosupport a range of communication modules that interface with the leadingcommunications networks already in use. Multiple candidate networks canbe used, and communications modules capable of communicating them arecommercially available.

As shown in FIG. 10, when sensor 1000 is installed on a powerdistribution line, the communication module it contains will have aunique physical address, such as a MAC address or similar. That addressis transmitted to the utility provider as part of the alert message,identifying sensor 1000 which originated the alert message. Eachindividual sensor 1000 is associated with the geographical location andserial number of the pole on which it is installed, so the alert messagewill inherently identify the geographical location of its origin.Because each sensor 1000 will be serialized for location recording attime of installation, a system user, such as a utility company will knowwhich pole the sensor is on and where to respond.

Again, the system controller coordinates all electrical functions withinsensor 1000. System controller 700 distributes power to the otherelements, monitors the load cell, controls the system logic, sendsstatus to the visual status indicator, and sends alerts to thecommunications module.

In a preferred embodiment of the sensor 1000, a microcontroller orequivalent, hosts the software that provides the logic which defines thesystem functionality. The microcontroller within the circuit cardreceives the following 3 input signals:

-   -   1. Current—in the form of power line current detection from        energy harvester 200;    -   2. Voltage—in the form of voltage detection from energy        harvester 200; and    -   3. Mechanical Load—in the form of a load cell voltage, from        strain gauges attached to load cell post 400.

Based on these inputs, the electronics provide output signals to thevisual status indicator and to remote system users to indicate, forexample:

-   -   1. The power line is mechanically and electrically sound; or    -   2. The power line is mechanically sound but un-energized; or    -   3. The power line is down but energized; or    -   4. The power line is down and un-energized; or    -   5. Pole damaged an energized; or    -   6. Pole undamaged, but energized.

The voltage and current signals are provided via the energy harvester,indicating that line voltage and current are either detected or notdetected. Because energy at any level on a downed power line is ahazard, detecting the presence of current and/or voltage is key;quantifying the values of current and/or voltage is an unnecessarycomplication. Tension alerts are generated by the system controller viathe load cell when the tension varies by more than the predeterminedvalue.

The present invention may further comprise an accelerometer added to thecontrol electronics to replace the load cell sensor to determine if thesensor has moved or changed orientation as the result of a downed line.If an event occurs, the accelerometer will sense if the sensor changesangle/orientation and then sensor can alert the user that an event hasoccurred. The energy harvester would indicate the presence of currentand/or voltage on the line so an alert can be sent that an event hasoccurred and whether the line is energized or not. The accelerometer canalso be used to determine if the sensor has moved, indicating that theutility pole cross arm has been broken. This information will beprovided to the user in the alert message so they know that additionalcrew may be needed to repair the damage.

The above-described embodiments are merely exemplary illustrations setforth for a clear understanding of the principles of the invention. Manyvariations, combinations, modifications, or equivalents may besubstituted for elements thereof without departing from the scope of theinvention. It should be understood, therefore, that the abovedescription is of an exemplary embodiment of the invention and includedfor illustrative purposes only. The description of the exemplaryembodiment is not meant to be limiting of the invention. A person ofordinary skill in the field of the invention or the relevant technicalart will understand that variations of the invention are included withinthe scope of the claims.

1. A wireless sensor apparatus for measuring status of an electricalwire, said sensor apparatus physically disposed in contact with saidwire and comprising: an electrically insulated housing; a means forwireless electrical energy harvesting, said means for wirelesselectrical energy harvesting disposed within said housing; a means forproviding electrical power to said sensor apparatus, said means forproviding electrical power operatively connected to said energyharvesting device; a programmable microprocessor, said microprocessoroperably connected to said apparatus; a means for measuring themechanical load on said housing, said means for measuring the mechanicalload on said housing operably connected to said microprocessor; a meansfor determining the presence of an electric current through saidelectrical wire, said means for determining the presence of an electriccurrent through said electrical wire operably connected to saidmicroprocessor; a means for determining the presence of an electricvoltage within said electrical wire, said means for determining thepresence of an electric voltage operably connected to saidmicroprocessor; a means for wireless data transmission, said means forwireless data transmission operably connected to said microprocessor; avisual display, said visual display operably connected to saidmicroprocessor.
 2. The wireless sensor of claim 1, wherein the insulatedhousing comprises HDPE.
 3. The wireless sensor of claim 1, wherein saidmeans for wireless electrical energy harvesting comprises anelectromechanical AC energy harvester.
 4. The wireless sensor of claim1, wherein said means for providing electrical power comprises arechargeable battery.
 5. The wireless sensor of claim 1, wherein thevisual display comprises a plurality of LEDs.